The present invention relates generally to needle selection devices for knitting machines and more specifically to a selection device that is electrically actuated and which is programmable by a selection tape or the like.
Although the selection device of the present invention may be used with any type of knitting machine, the present selection device was specifically invented for a circular knitting machine such as model KIM made by Masriera S. A., Malgrat de Mar (Barcelona), Spain, a description of which was printed in KNITTING TIMES -- May 27, 1974 and KNITTING INTERNATIONAL -- June, 1974. The KIM machine, which has a rotating dial and cylinder and a stationary cambox and yarn stand, is presently being made in 10 inch and 12 inch diameters with four feeds, preferrably having 280 needles. Virtually all of the functions of the machine are controlled from a main control chain which works with a series of microswitches, one for each of the 24 functions of the machine. The machine is provided with four feeder knitting stations. A pattern drum for controlling the needle selection is disposed at each feeder station on the machine. The pattern drum contains 24 slots around its circumference and can either take 24 clavettes in each of the slots or individually placed pegs, also 24 high. the clavettes or pegs coact with 24 selectors at each feed, which in turn select the jacks mounted in the cylinder of the knitting machine so as to position associated needles that are required for the knitting process to provide a predetermined knitting pattern.
The predetermined knitting pattern of the KIM knitting machine is limited in size, both in length and width. Since the pattern drum contains 24 steps, the pattern area is either 24 or 49 wales wide depending on whether the 24 step needle jacks that are working in conjunction with the drum are set out in a diagonal formation or a V-formation. The depth of the design is 96 courses with the 24 slot drum. Therefore, if a larger predetermined knitting pattern is desired, the pattern drum must be made larger to contain more slots around its circumference and its vertical length must be increased to provide a greater number of steps for each slot. It is evident that increasing the size of the pattern drum requires that the size of the knitting machine itself be greatly increased.
The cylinder of the KIM machine is provided with alternating needles and pattern elements about its circumference. Pattern jacks are provided beneath both the needles and the pattern elements and the selection process for both the needles and the pattern elements is essentially the same. Selection of the knitting elements is made by the use of jacks in a conventional manner. At the exit of a previous feeding station, the needles and the jacks are cammed down by cams acting on the needle butts. The jacks are disposed within slots around the circumference of the cylinder and may either be pulled out of their associated slots so that their butts protrude or may be pushed in so that their butts lie within their slots. Accordingly, only the non-selected needles have their jacks left protruding from the needle cylinder. The jacks which remain protruding are raised by a cam which raises the corresponding needle or pattern element into the operating position within its slot. Needle selection within the cylinder is carried out by a pattern mechanism which acts on the above-mentioned jacks. The pattern mechanism, which is provided at each feed station, comprises two drums having removable pins. One of the drums is relatively large and has 24 racks or slots. The large drum controls the needle selection for the patterning sequence. The relatively smaller drum, which has 18 slots, controls the needles during the formation of the rib cuffs, etc. The pattern mechanism is arranged so that a pin that is placed in the relatively large pattern drum will push in the jack to cause a needle not to knit to thereby obtain a desired knitting pattern. However, a pin placed in the relatively small drum overrides the pattern drum and causes the needles not to knit regardless of the larger drum. Thus, the larger drum can be used to control the needle selection for the body design whereas the smaller drum is used primarily to select needles for knitting cuffs.
A recently patented example of a prior art knitting selection arrangement for a knitting machine is disclosed in U.s. Pat. No. 3,961,501, granted on June 8, 1976 to Johann Martinetz. The structure disclosed in the Martinetz patent relates to needle selecting arrangements for knitting machines of the type wherein the needle selection is effected by energizing or de-energizing control members that are comprised of materials which undergo dimensional changes, for example, piezoelectric, electrostrictive, magnetostrictive, or bimetallic control members and the like. A cam position control arrangement in the Martinetz patent includes at least one cam position control member that is comprised of one of the foregoing materials that is capable of undergoing dimensional changes. Upon the application of an energizing signal to the control member, the control member undergoes a dimensional change thereby causing the control member to control the position of the selecting cam arrangment. In the Martinetz structure, a plurality of elongated force-transmitting members may be included with one being provided for each motion transmitting portion. Control cams are mounted for movement relative to the carrier, or vice-versa and are operative for effecting longitudinal movement of the force transmitting member to a position causing respective motion-transmitting members to assume one of their respective positions. A biasing spring urges the force-transmitting member back in the opposite direction and a detent that may also be made of a piezoelectric material is energizable or de-energizable in order to assume a position locking the force transmitting member in the activated position thereof against the returning force of the biasing spring.
The piezoelectric structure in the Martinetz patent can be shaped and positioned so as to effect a needle selecting operation utilizing the characteristic of the piezoelectric materials which permits it to be alternately activated and de-activated with very high frequency. However, one of the disadvantages of the piezoelectric material is that the actual force that it can directly bring to bear is not great, compared to the force which can be exerted by an electromechanical relay. In the Martinetz patent this obvious and well known limitation of the piezoelectric material is overcome by exploiting the combined action of a plurality of such piezoelectric control members and/or by making use of such control members in needle selecting arrangements where the control members are not called upon to create the actual force which moves the motion-imparting portions of the needle units into engagement with the lifting and lowering cams. Another substantial disadvantage of the use of piezoelectric materials is that the extent of the dimensional change or deflection thereof is not accurately controlled either in magnitude or direction.